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Measurements have been made of the effects of low-energy electron bombardment (0–300 ev) on a chemisorbed layer of oxygen on polycrystalline molybdenum. Oxygen is adsorbed in two states at room temperature with approximate heats of adsorption of 60 and 110 kcal/mole, respectively. O+ ions are released from the weakly bound state with a maximum probability of 10−5 ion/electron at an electron energy of 90 ev. The ion-energy distribution, measured by a retarding-field method, has a maximum at about 6 ev and a half-width of 5 ev. About 50 neutrals are released for every ion. The measured threshold energy, 17.6 ± 0.2 ev, for ion formation is in good agreement with the calculated value. The probability of ion and neutral release from the strongly bonded state is about 2 × 103 times smaller than for the weakly bonded state. A qualitative explanation of the formation of neutrals is proposed in terms of Auger neutralization of the ions near the surface. Reflection of the ion-energy distribution in the calculated curve of the potential energy of the O+ ion yields, after correction for Auger neutralization, the probability density distribution of the adsorbed oxygen atom. The equilibrium spacing of the chemisorbed atom is then estimated to be 1.67 Å.

The adsorption of carbon monoxide on polycrystalline tungsten wires has been studied by a modified flash-filament method under ultra-high-vacuum conditions. Adsorption occurs in several phases with differing heats of adsorption; the lowest energy phase (with a heat of 29 kcal/mole) is interpreted as a " gap-filling " phase with a double bond to a single tungsten atom. The various higher energy phases are interpreted as the result of the formation of bridged bonds, between a carbon monoxide molecule and two tungsten atoms, on the different crystal faces exposed. The initial sticking probability and total coverage are found to be constant, in the temperature range 300°K to 600'K, at about 0.5 and 9.5 x 1014 molecules/cm2 respectively. The adsorption rate as a function of coverage is shown to be in approximate agreement with the theory of Kisliuk for doublesite adsorption into an immobile film.

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An approximate theory is developed of the breakdown characteristics of a coaxial diode in an axial magnetic field, taking into account the effects of elastic collisions. It is assumed that the electron moves in a constant electric field between collisions and thus the theory is valid only in the appropriate range of magnetic field and voltage. Estimates of transit time and of space-charge effects are also made. Measurements in the pressure range 10−3 to 10−9 mm. Hg are in general agreement with the theory.